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peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 15/05/2021 Benznidazole, the primary drug used in Chagas’ disease treatment, has known side effects, which may limit its widespread use. Its low solubility could negatively interfere in the bioavailability, even accentuating the toxic effects. Cocrystals have been extensively used to modify and optimize physicochemical properties, but, as single-component raw materials, they are susceptible to the phenomenon of polymorphism. In this work, we report a trimorphic cocrystal containing a 1:1 ratio of benznidazole and salicylic acid. The crystalline structures of three polymorphs were elucidated by single-crystal X-ray diffraction. Moreover, several isostructural solvates were also synthesized and analyzed. The same carboxylic acid-imidazole supramolecular heterosynthon is present in the four forms, but the main structural feature is an extended column based on amide-amide hydrogen bonds. Based on the crystalline structures, the trimorphic system was classified as conformational and packing polymorphism. Furthermore, the dissolution profiles of the stable forms were determined and shown a significant solubility improvement over the raw material.

peer-reviewed Acetylene (C2H2) capture is a step in a number of industrial processes but comes with a high energy footprint. Whereas physisorbents have the potential to reduce this energy footprint, they are handicapped by generally poor selectivity vs. other relevant gases such as CO2 and C2H4. In the case of CO2, the respective physicochemical properties are so similar that traditional physisorbents such as zeolites, silica and activated carbons cannot differentiate well between CO2 and C2H2. Herein we report that a family of three isostructural, ultramicroporous (< 7 Å) diamondoid metal-organic frameworks, [Cu(TMBP)X] (TMBP = 3,3',5,5'tetramethyl-4,4'-bipyrazole), TCuX (X = Cl, Br, I), offer new benchmark C2H2/CO2 separation selectivity at ambient temperature and pressure. We attribute this performance to a new type of strong binding site for C2H2. Specifically, halogen…HC interactions coupled with other noncovalent in a tight binding site is C2H2-specific vs. CO2. The binding site is distinct from those found in previous benchmark sorbents, which are based upon open metal sites or electrostatic interactions enabled by inorganic fluoro or oxo anions.

Dynamic and flexible metal–organic frameworks (MOFs) that respond to external stimuli, such as stress, light, heat, and the presence of guest molecules, hold promise for applications in chemical sensing, drug delivery, gas separations, and catalysis., Dynamic and flexible metal–organic frameworks (MOFs) that respond to external stimuli, such as stress, light, heat, and the presence of guest molecules, hold promise for applications in chemical sensing, drug delivery, gas separations, and catalysis. A greater understanding of the relationship between flexible constituents in MOFs and gas adsorption may enable the rational design of MOFs with dynamic moieties and stimuli-responsive behavior. Here, we detail the effect of subtle structural changes upon the gas sorption behavior of two “SIFSIX” pillared square grid frameworks, namely SIFSIX-3-M (M = Ni, Fe). We observe a pronounced inflection in the Xe adsorption isotherm in the Ni variant. With evidence from X-ray diffraction studies, density functional theory, and molecular simulations, we attribute the inflection to a disordered to ordered transition of the rotational configurations of the pyrazine rings induced by sorbate–sorbent interactions. We also address the effect of cage size, temperature, and sorbate on the guest-induced ring rotation and the adsorption isotherms. The absence of an inflection in the Xe adsorption isotherm in SIFSIX-3-Fe and in the Kr, N2, and CO2 adsorption isotherms in SIFSIX-3-Ni suggest that the inflection is highly sensitive to the match between the size of the cage and the guest molecule.

peer-reviewed Inspired by the structure of carbonic anhydrase, we developed a robust ultramicroporous lanthanide metal-organic framework (MOF) platform (NKMOF-3-Ln), which possess porous pocket to selectively bind with CO2 at ambient condition. Notably, CO2 molecules can be precisely observed in the single crystal structure of NKMOF-3-Ln. Highly ordered CO2 molecules can strongly interact with framework via electrostatic interaction of nitrates. We found that the CO2 adsorption capacity and binding energy were gradually enhanced as lanthanide contracting. The strong CO2 binding affinity endows NKMOF-3-Ln excellent CO2 separation performance, verified by experimental breakthrough results. Moreover, ascribed to the specific binding affinity of CO2, NKMOF-3-Eu showed fluorescence response to CO2.